This invention is directed to a heat sink, and more specifically a heat sink for dissipating heat from a heat source by magnetically enhanced convection.
Dissipating heat from electrical and electronic systems and devices is a technical issue affecting cost and performance throughout the electronic industry. With respect to the aerospace industry in particular, where the use of electronic devices is prevalent, the problem of dissipating heat from these devices is of major concern due to the limitations on space and available power. In the absence of gravity aboard orbiting spacecraft, heat dissipation must rely on radiative or conductive transport, forced convection, or heat pipes. Radiation is inefficient at low and moderate temperatures such as those encountered aboard the International Space Station or other space craft. Conduction is usually inefficient, and even when efficient it imposes a mass penalty in the form of metal conduction paths. Forced convection requires the use of power which is at a premium in many aerospace and other applications, and often generates undesirable vibration and noise. Heat pipes usually cannot be used within an electronics assembly.
Heat sinks for electronics commonly use all three types of heat dissipation or transport, i.e., radiation, conduction, and convection. A typical heat sink is a black, finned mass of aluminum that is bolted or glued to the electronic device. Typically, such heat sinks have a rough black surface to enhance the radiative heat rejection. The use of fins on the heat sink improves contact with the air, and therefore enhances convection heat rejection. The choice of aluminum gives high thermal conductivity from the electronic device to the fins and radiating surfaces. Also, there is a small amount of conduction through the air itself. In many cases, conduction through the air is insignificant, and radiant heat rejection is often insufficient when temperatures are kept within the operating temperature range of most electronics. Furthermore, radiant transfer is often reduced due to the presence of other hot radiating surfaces within the heat sink's field of operation. Thus, convection is the means most often used to accomplish the required heat rejection.
Cost and performance drive electronic designers to increase the packing density of electronic components on circuit boards and within individual chips. This increases the heat generated per unit area. To increase convective heat rejection enough to meet the increased load, designers often use fans to force a higher flow rate of air over the circuit. However, cooling fans add noise, cost, weight, and power usage, and represent one of the major sources of failure in modern avionics. In some cases requiring extremely high packing density, designers use a circulating liquid to radically increase convective transfer from a circuit. However, the requisite fluid pumps, hoses, and chillers add greatly to system mass, cost, and maintenance needs. The problem of providing sufficient convection is particularly acute where the electronics are operating in a microgravity environment, such as an orbiting space craft, where gravity-driven convection is not present.
This invention addresses and overcomes these problems by providing an apparatus and method for enhancing convection cooling of electronic devices by the use of magnetothermal convection (MTC).